I haven’t read every single post, but here are nevertheless my thoughts:
I love "A.I.". I even wrote my master's thesis about it. If the ending of the movie is a happy ending or not depends very much on how you "read" the movie. For me, it wasn't.
The conflict of the movie is established very early: It's all about the qustion wether or not there should be robots with the ability to love and if humans could deal with the responsibility that arises from that. And the answer the movie gives - at least for me- is: No, humans are incapable. They fail on every level in this movie. They destroy the planet, they destroy themselves. Davids human mother clearly wasn’t up for the task to “raise” both, her own boy, and David. Both parents were afraid of David or at least saw danger in him. They couldn’t treat him as someone equal. He was always just a machine for them. So, instead of working through their problems, they just “dumbed” him, even though David had real feelings. But because David was programmed the way that he sought his mother’s love he went on a journey in order to find it. And when he finally saw his mother again in the future, all he got is a “faked” love, because the real mother has died centuries ago. Future-Monica was just a copy. So her love is an illusion.